1. Field of the Invention
The present invention relates in general to vehicular headlamps, and more particularly, to vehicular headlamps of a type which has respective light sources for high and low beams projected therefrom.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional vehicular headlamp of the above-mentioned type will be described with reference to FIGS. 9 to 11 of the accompanying drawings.
The conventional headlamp is shown in FIGS. 9 and 10, which is generally designated by reference "a" and comprises a concave light reflector "b" which has a light reflecting surface "c" of paraboloid of revolution with a focus at the point "F". The light reflector "b" has an opening shaped generally rectangular.
Designated by reference "d" is a filament for a high beam, which is located below the focus "F" of the light reflecting surface "c" at a somewhat left side of the same, as viewed from the front of the headlamp "a". The filament "d" extends substantially horizontally in a direction perpendicular to a rotation axis "x-x" of the light reflecting surface "c". It is to be noted that the rotation axis is the imaginary axis about which a parabolic line is rotated for formation of the light reflecting surface "c".
Designated by reference "e" is a filament for a low beam, which is located above the focus "F" at a somewhat right side of the same, as viewed from the front of the headlamp "a". Similar to the filament "d" for the high beam, the filament "e" extends substantially horizontally in a direction perpendicular to the rotation axis "x-x" of the light reflecting surface "c".
A lens (not shown) is positioned in front of the concave light reflector "b".
When, in operation, the filament "d" for the high beam is energized and thus produces a light, the headlamp "a" projects a light beam which has such a contoured beam pattern "f" as shown in FIG. 11A.
It is to be noted that the pattern "f" is an illuminated image shown on a screen which is positioned in the front of the headlamp "a". The line "H-H" is the horizontal line which extends through a point corresponding to the center of the headlamp "a", and the line "V-V" is the vertical line which extends through the point.
While, when the filament "e" for the low beam is energized to produce a light, the headlamp "a" projects a light beam which has such a contoured beam pattern "g" as shown in FIG. 11B.
However, due to its inherent construction, the headlamp "a" has the following drawbacks.
Since, in the high beam pattern, the intersecting portion (pointed by the finger mark 1) of the horizontal and vertical lines "H-H" and "V-V" is positioned away considerably from the center of the high beam pattern "f", the illumination degree at the intersecting portion is lowered thereby making the long distance illuminating ability very poor. Furthermore, since the portion pointed by the finger mark 2 is supplied with substantially no light, the middle distance illuminating ability of the headlamp "a" is also poor.
Furthermore, since the low beam pattern "g" has no illuminated zone at the portion pointed by the finger mark 3, the neighbouring illuminating ability of the headlamp is poor.